Wire rope

ABSTRACT

A wire rope for use in a medical procedure includes a multi-strand coil formed by twisting multiple metal wires together. In the wire rope, gaps are located between the multiple metal wires along an axis of the multi-strand coil. The gaps between the multiple metal wires include a first gap and a second gap that differ in width.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2011-279058 filed in the Japan Patent Office on Dec. 20, 2011, theentire contents of which are incorporated herein by reference.

BACKGROUND

The disclosed embodiments relate to a medical device. More specifically,the disclosed embodiments relate to wire ropes. Wire ropes aremulti-strand coils formed by twisting multiple wires together (see FIG.7). Japanese Unexamined Patent Application Publication No. 9-49517discloses a structure of a flexible shaft including a core shaft. Inthis structure, wires are each helically wound around the core shaftwhile having minute gaps between turns of the wires, Japanese UnexaminedPatent Application Publication No. 2001-280333 discloses a flexibleshaft in which at least one of an outer-layer wire and an inner-layerwire is wound while having regular gaps between turns of the wire.Japanese Unexamined Patent Application Publication No. 7-14448 disclosesa method of manufacturing a multilayer cable in which multiple corewires, serving as an inner layer, are twisted together in a directionthat is opposite to the direction in which multiple core wires, servingas an outer layer, are twisted together.

SUMMARY

However, the existing wire ropes, particularly the multi-strand coils,have the following drawbacks. When a force is applied to a wire rope insuch a direction as to twist or untwist the wire rope around the axiswhile the wire rope is bent, the wires are heated by frictional heat dueto the wires rubbing against each other or by heat due to plasticdeformation. Thus, the wires may become deformed or cut.

The flexible shaft disclosed in Japanese Unexamined Patent ApplicationPublication No. 9-49517 has excellent flexibility since gaps areprovided between turns of each wire. However, each of the layers of theflexible shaft is constituted by a single wire. Thus, when the flexibleshaft is bent and is twisted around, heat is generated in the shaft andthe wires may be cut as a result of the heat generated. Moreover,cutting the wires severely degrades the durability of the flexible shaftand the flexible shaft may be broken.

In the flexible shaft disclosed in Japanese Unexamined PatentApplication Publication No. 2001-280333, the wires are wound whilehaving gaps between some adjacent turns of the wires in the longitudinaldirection. However, the remaining part, other than the one wound withthe gaps, is tightly wound. Since the tightly wound part of the wires ofthe flexible shaft suffers from heat generated therein, the durabilityof the whole flexible shaft is greatly reduced.

In the cable disclosed in Japanese Unexamined Patent ApplicationPublication No. 7-14448, the wires are each wound with no gaps betweenturns. Thus, the cable is more likely to experience increased heat, andtherefore also exhibits reduced durability, as in the flexible shaftsdescribed in Japanese Unexamined Patent Application Publication Nos.9-49517 and 2001-280333.

Embodiments of the present invention are made in view of theabove-discussed circumstances. Therefore, an object of the exemplaryembodiments is to provide a wire rope that has excellent durability andexcellent flexibility by reducing, or preventing wires from rubbingagainst each other to thereby suppress heat generation.

In an aspect, a wire rope includes a multi-strand coil formed bytwisting a plurality of metal wires together, and gaps are locatedbetween the plurality of metal wires along an axis of the multi-strandcoil.

By providing gaps between the metal wires in this manner, adjacent metalwires are less likely to interfere with one another and thus the wirerope bends easily. Moreover, if, for example, torque is applied alongthe axis of the wire rope by bending the wire rope, the metal wires areless likely to come into contact with one another and thus heatgeneration due to friction can be prevented. Consequently, the wire ropeaccording to the disclosed embodiments of the present invention exhibitshigher durability than the existing wire ropes.

The wire rope according to the embodiments of the present invention hashigher durability and excellent flexibility by gaps being providedbetween turns of each of metal wires to prevent heat generation due tofriction between the metal wires when the wires are bent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a wire rope according to a firstembodiment when viewed in vertical section.

FIG. 2A is a graph showing performance test results of both the wirerope according to the embodiments of the present invention and a relatedart wire rope.

FIG. 2B is a schematic diagram of a configuration for the test depictedin FIG. 2A.

FIG. 3 schematically illustrates a wire rope according to a secondembodiment when viewed in vertical section.

FIG. 4 schematically illustrates a wire rope according to a firstmodification of the second embodiment when viewed in vertical section.

FIG. 5 schematically illustrates a wire rope according to a secondmodification of the second embodiment when viewed in vertical section.

FIG. 6 schematically illustrates a wire rope according to a thirdmodification of the second embodiment when viewed in vertical section.

FIG. 7 schematically illustrates a related art wire rope when viewed invertical section.

DETAILED DESCRIPTION OF EMBODIMENTS

Wire ropes according to embodiments of the present invention will bedescribed referring to the drawings.

As illustrated in FIG. 1, a wire rope 1A according to a first embodimentof the present invention includes a multi-strand coil 10 formed bytwisting multiple metal wires 11 together. The materials of the metalwires 11 are not limited to any particular type of material, so long asthe materials exhibit high hardness. Accordingly, the materials of themetal wires may include, but are not limited to stainless steel wires,carbon steel wires, steel wires for springs, or any other metalexhibiting a hardness that is at least as high as the hardness of steel.

Gaps are located between the metal wires 11 of the multi-strand coil 10along the axis of the multi-strand coil 10. Accordingly, the metal wires11 are arranged so that the metal wires do not contact one another(i.e., without touching each other).

For instance, in one embodiment, such as the one depicted in FIG. 1, thegaps between the metal wires 11 include gaps d1 and d2 that differ inwidth. Specifically, the gaps between the metal wires 11 include narrowgaps d1 and wide gaps d2, which are wider than the narrow gaps d1.

As described above, locating gaps between the metal wires 11 improvesthe flexibility of the wire rope 1A. This is because, when the wire rope1A is bent, the metal wires 11 easily approach one another withoutinterfering with one another at the inner side of the bent portion. If,for example, torque is applied along the axis of the wire rope 1A bybending the wire rope 1A, the metal wires 11 are less likely to comeinto contact with one another. This prevents heat generation due tofriction between the metal wires 11 and prevents the metal wires 11 frombeing cut or suffering from other defects. Thus, the durability of thewire rope 1A improves.

The gaps between the metal wires 11 may include gaps of varying width.For instance, as shown in FIG. 1, the metal wires 11 may include narrowgaps d1 and wide gaps d2 that differ in width. Thus, if the wire rope 1Ais bent into various shapes, the metal wires 11 can be flexibly deformedin accordance with these shapes. Thus, the wire rope 1A has a favorableflexibility and heat generation due to friction can be reliablyprevented.

Referring now to FIGS. 2A and 2B, a durability test for wire ropes andthe results of the test will be described. Wire ropes 1A according tothe first embodiment and wire ropes 100 according to a related art (seeFIG. 7) were used for the test. In the test, the durability of the wireropes was measured under the following conditions. As illustrated inFIG. 2B, the wire ropes were bent, with one end of each wire rope beingconnected to a motor, and the other end of the wire rope being connectedto a brake. The motor was driven in order to consecutively apply torquealong the axis of the wire rope. Tests were conducted under thefollowing conditions: the diameters of bent portions R were set at 40mm, 45 mm, and 50 mm; the rotational speed of the motor was 1800 (rpm);and the braking force was 20 (N·mm). The test was conducted untilaudible failure from the tested wire rope was heard, and the time atwhich audible failure was heard was recorded as the durability (sec).

FIG. 2A shows the test results. The durability of both the wire rope 1Aaccording to the first embodiment and the wire rope 100 according to therelated art both increased, as the diameter of the bent portion R of thetested wire rope became larger. However, the durability of the wireropes 1A according to the first embodiment was approximately 200%, atmaximum, of the durability of the corresponding wire ropes 100 accordingto the related art. That is, the observed durability of the wire ropes1A according to the first embodiment was nearly double that of the wireropes 100 according to the related art. The durability of the wire ropes1A according to the first embodiment exhibited superior durabilityresults to those of the related art for at least the following reasons.The metal wires 11 of the wire ropes 1A are less likely to rub againsteach other, therefore heat generation due to friction between the metalwires 11 is prevented, and thus the metal wires 11 are prevented frombeing cut.

The gaps between the metal wires 11 need not be limited to anyparticular configuration. For instance, in alternate embodiments thewire rope 1A may include gaps of uniform width between the metal wires11. However, in order for the metal wires 11 to be flexibly deformablein accordance with various shapes into which the wire rope 1A is bent,it is preferable that the gaps between the metal wires 11 include thenarrow gaps d1 and the wide gaps d2 that differ in width.

The arrangement of successive narrow gaps d1 and wide gaps d2 may vary.For instance, as illustrated in FIG. 1, the wire rope 1A may have aportion in which multiple narrow gaps d1 are successively formed and aportion in which multiple wide gaps d2 are successively formed. However,in other embodiments, the narrow gaps d1 and the wide gaps d2 may bealternately formed or may be formed at random.

From the view point of flexibility of the metal wires 11 with which themetal wires 11 are deformable in accordance with various shapes intowhich the wire rope 1A is bent, it is preferable that the narrow gap d1and the wide gap d2 are formed alternately or at random. In the firstembodiment, other gaps whose width differs from those of the narrow gapsd1 and the wide gaps d2 may be further provided between the metal wires11.

Referring to FIG. 3, a second embodiment will be described now. Portionsthat are the same as those in the first embodiment will not be describedand the same portions are denoted by the same reference numerals.

As illustrated in FIG. 3, a wire rope 1B according to a secondembodiment of the present invention includes a multi-strand coil 10 anda multi-strand coil 20 that is disposed inside the multi-strand coil 10.Hereinbelow, the multi-strand coil 10 disposed on the outer side isreferred to as an outer multi-strand coil 10, and the multi-strand coil20 disposed on the inner side is referred to as an inner multi-strandcoil 20.

The outer multi-strand coil 10 is wound around the outer circumferenceof the inner multi-strand coil 20. The multi-strand coils 10 and 20 arearranged such that the outer multi-strand coil 10 is wound in the samedirection as the inner multi-strand coil 20. A winding angle α, at whichthe outer multi-strand coil 10 is wound when viewed in vertical section,is made different from a winding angle β, at which the innermulti-strand coil 20 is wound when viewed in vertical section.Specifically, the winding angle α is formed between the center line CLof the wire rope 1B when viewed in vertical section and the center lineof each metal wire 11 of the outer multi-strand coil 10, and the windingangle β is formed between the center line CL of the wire rope 1B whenviewed in vertical section and the center line of each metal wire 21 ofthe inner multi-strand coil 20.

As described above, winding the outer multi-strand coil 10 and the innermulti-strand coil 20 in the same direction negligibly distorts themulti-strand coils 10 and 20 when torque is applied to the wire rope 1B.Thus, the entirety of the wire rope 1B has a higher torque resistance.In addition, the multi-strand coils 10 and 20 are in point contact withone another since the winding angle α of the outer multi-strand coil 10and the winding angle β of the inner multi-strand coil 20 are differentfrom each other. Consequently, the metal wires 21 of the innermulti-strand coil 20 are prevented from entering the gaps between themetal wires 11 of the outer multi-strand coil 10. In this embodiment,the winding angle α of the outer multi-strand coil 10 is larger than thewinding angle β of the inner multi-strand coil 20. Thus, tension in thelongitudinal direction of the metal wires 11 of the outer multi-strandcoil 10 can be reduced. This can reduce fatigue of the metal wires 11 ofthe outer multi-strand coil 10 and the wire rope 1B can thereforeexhibit a higher durability.

A first modification of the second embodiment will be described now.

As illustrated in FIG. 4, a wire rope 1C according to the firstmodification includes an outer multi-strand coil 10 and an innermulti-strand coil 20, which are wound in the same direction. The windingangle α of the outer multi-strand coil 10 when viewed in verticalsection is smaller than the winding angle β of the inner multi-strandcoil 20 when viewed in vertical section.

If torque is applied to the wire rope 1C having the above-describedconfiguration, the multi-strand coils 10 and 20 are less likely to bedistorted and the entirety of the wire rope 1C has a higher torqueresistance. In addition, since the multi-strand coils 10 and 20 are inpoint contact with one another, the metal wires 21 of the innermulti-strand coil 20 are prevented from entering the gaps between themetal wires 11 of the outer multi-strand coil 10.

A second modification of the second embodiment will be described now.

As illustrated in FIG. 5, in a wire rope 1D according to the secondmodification, a space s is provided between the inner circumference ofan outer multi-strand coil 10 and the outer circumference of an innermulti-strand coil 20.

The wire rope 1D having this configuration can be easily bent becausemetal wires 11 of the outer multi-strand coil 10 and metal wires 21 ofthe inner multi-strand coil 20 are less likely to interfere with oneanother. If torque is applied along the axis of the wire rope 1D bybending the wire rope 1D, heat generation due to friction is morereliably prevented. Thus, the wire rope 1E can have a higher durability.

A third modification of the second embodiment will be described now.

As illustrated in FIG. 6, in a wire rope 1E according to the thirdmodification, gaps d11 and d12 between metal wires 11 of an outermulti-strand coil 10 are wider than gaps d13 between metal wires 21 ofan inner multi-strand coil 20.

The wire rope 1E having this configuration is more easily bent. Iftorque is applied along the axis of the wire rope 1E by bending the wirerope 1E, heat generation due to friction can be more reliably prevented.Thus, the wire rope 1E can have a higher durability.

The embodiments of the present invention are not limited to theabove-described embodiments and the embodiments may be modified orcombined as appropriate within a scope not departing from the gist ofthe invention.

The gaps d1, d2, d11, and d12 between the metal wires 11 may be providedat least at main portions of the wire ropes 1A to 1E, the main portionsbeing deformable into curves in the longitudinal direction.

The ranges for the diameter of the individual wires 11 may range from0.25 mm to 0.30 mm. The diameter of the wire rope may range from 1.2 mmto about 1.5 mm. The gap d1 may range from 0.5 mm to 0.15 mm. The gap d2may range from 0.15 to 0.25 mm. As such, gaps d1 and d2 may havedifferent dimensions, and may in fact have any range of dimensions, aslong as d1 and d2 are randomly located in an axial direction of rope.The diameter of the inner wire rope may range from 0.6 mm to 1.0 mm,while the diameter of the individual inner wires 21 may range from 0.10mm to 0.25 mm. The winding angles may vary. For instance, winding angleα may vary from 45° to 75°, while winding angle β may range from 45° to75°. The diameter for the inner wire rope may range from 0.50 mm to 0.85mm. The gaps d11, d12 and d13 may range from 0.12 mm to 0.15 mm; 0.15 mmto 0.25 mm; and 0.04 mm to 0.11 mm, respectively

The wire ropes 1A to 1E are each preferably usable as a component oftools, such as an endoscopic surgical tool in which a driving core shaftis inserted into the outer multi-strand coil 10 and the innermulti-strand coil 20, or as a component of an industrial component.

What is claimed is:
 1. A wire rope for use in a medical procedure, thewire rope comprising: a first multi-strand coil including a plurality ofmetal wires, wherein the first multi-strand coil has gaps between theplurality of metal wires along an axis of the first multi-strand coil.2. The wire rope according to claim 1, wherein the gaps between theplurality of metal wires include a first gap and a second gap thatdiffer in width.
 3. The wire rope according to claim 1, furthercomprising: a second multi-strand coil, wherein the second multi-strandcoil is disposed inside the first multi-strand coil such that the firstmulti-strand coil on an outer side is wound around an outercircumference of the second multi-strand coil on an inner side, andwherein the first multi-strand coil on the outer side is wound in thesame direction as the second multi-strand coil on the inner side, and anangle at which the first multi-strand coil on the outer side is woundwhen viewed in vertical section differs from an angle at which thesecond multi-strand coil on the inner side is wound when viewed invertical section.
 4. The wire rope according to claim 2, furthercomprising: a second multi-strand coil, wherein the second multi-strandcoil is disposed inside the first multi-strand coil such that the firstmulti-strand coil on an outer side is wound around an outercircumference of the second multi-strand coil on an inner side, andwherein the first multi-strand coil on the outer side is wound in thesame direction as the second multi-strand coil on the inner side, and anangle at which the first multi-strand coil on the outer side is woundwhen viewed in vertical section differs from an angle at which thesecond multi-strand coil on the inner side is wound when viewed invertical section.
 5. The wire rope according to claim 3, wherein theangle at which the first multi-strand coil on the outer side is woundwhen viewed in vertical section is larger than the angle at which thesecond multi-strand coil on the inner side is wound when viewed invertical section.
 6. The wire rope according to claim 4, wherein theangle at which the first multi-strand coil on the outer side is woundwhen viewed in vertical section is larger than the angle at which thesecond multi-strand coil on the inner side is wound when viewed invertical section.